The Florida judge overseeing Casey Anthony’s murder trial is allowing novel smell evidence that has never been introduced in a criminal case.

Orlando prosecutors are seeking to prove that the bad smell in the trunk of Casey Anthony’s car came from a decomposing body rather than a bag of garbage, as the defense contends, the Associated Press reports.

Toward that end, prosecutors are introducing testimony by researcher Arpad Vass of Oak Ridge National Laboratory, the story says. Vass took an air sample from the car’s carpet and injected it into a gas chromatography/mass spectrometric to identify substances it contained. Then he compared them to chemicals identified in his research of decomposing bodies at a facility dubbed the Body Farm.

Testifying on Monday, Vass said he found “unusually high levels” of chloroform in the air from the carpet sample, a chemical associated with decomposition, the Orlando Sentinel reports. He also said his own sense of smell detected human decomposition.

Casey’s father, former police officer George Anthony, had told a 911 operator that the trunk of Casey’s car smelled like death when he reported that 2-year-old Caylee Anthony was missing.